Allow assertions to be enabled in Blink Release builds.

Source/core/html/parser/BackgroundHTMLInputStream.h

 /*
  * Copyright (C) 2013 Google, Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 42 matching lines @@
     size_t totalCheckpointTokenCount() const { return m_totalCheckpointTokenCount; }
 
 private:
     struct Checkpoint {
         Checkpoint(const SegmentedString& i, size_t n, size_t t) : input(i), numberOfSegmentsAlreadyAppended(n), tokensExtractedSincePreviousCheckpoint(t) { }
 
         SegmentedString input;
         size_t numberOfSegmentsAlreadyAppended;
         size_t tokensExtractedSincePreviousCheckpoint;
 
-#ifndef NDEBUG
+#if ENABLE(ASSERT)
         bool isNull() const { return input.isEmpty() && !numberOfSegmentsAlreadyAppended; }
 #endif
         void clear() { input.clear(); numberOfSegmentsAlreadyAppended = 0; tokensExtractedSincePreviousCheckpoint = 0;}
     };
 
     SegmentedString m_current;
     Vector<String> m_segments;
     Vector<Checkpoint> m_checkpoints;
 
     // Note: These indicies may === vector.size(), in which case there are no valid checkpoints/segments at this time.
     size_t m_firstValidCheckpointIndex;
     size_t m_firstValidSegmentIndex;
     size_t m_totalCheckpointTokenCount;
 
     void updateTotalCheckpointTokenCount();
 };
 
 }
 
 #endif